Metallurgy of zinc.



CHARLES VICTOR THIERRY, OF PARIS, FRANCE.

METALLURGY OF ZINC.

No Drawing.

Specification of Letters Patent.

Application filed November 2, 1911. Serial No. 658,142.

Patented June 25, 1912.

To all whom it may concern: a

Be it known that I, CHARLES VICTOR THIERRY, engineer, a citizen of the French Republic, and residing at 48 Ruede Malte,

I Paris, Department of the Seine, France,

have invented certain new and useful Improvements in or Relating to the Metallurgy of Zinc, of which the following is a specification.

It is well known that the condensation of liquid zinc from zinc vapor presents, from the point of view of the methods of working actually in use, very considerable difiiculties. For example only a portion of the vapors of zinc which are given off, are condensed in the form of liquid zinc, the remainder being deposited in the form of dust, known as blue-powder. Hitherto this difiiculty in the metallurgy of zinc has not been overcome, no matter what the product from which the zinc is distilled. Attempts to treat directly, either in the reverberatory furnace or cupola furnace, zinc ore to distil metallic Zinc have not succeeded because in all cases almost all the zinc was recovered either in the form of blue-powder or of oxids containing zinc. As there is a very limited field of employment for the powder and its commercial value is inferior to that of zinc, it has been necessary up to the present to reduce as much as possible the quantity of powder obtained. Many other methods have been tried to reduce the amount of powder, for example: 1. By diminishing the charge. 2. By using besides coke or coal for reduction, other deoxidizing products. 3. By modifying in an appropriate manner the form of the condensers. 4. By regulating carefully the temperature of the condensers. These means, and particularly the first, are inconvenient from the point of view of the economical Working of the furnace. They render the working difficult and complicated to such a degree that it is only by making concessions from this point of view that a condensation can be obtained as complete as possible in the form of liquid zinc. From these facts in consequence of the difficulty which exists to find a use for the powder, it will be seen that a process by which it can be converted directly into metallic zinc will present important advantages. This inven-\ tion is for a process for treating blue-powder which has been obtained, either as a product in the course of the usual operation of zinc distillation, or as a product in the course of an operation by which it is obtained directly.

The invention is based upon the observation that the powder consists of very small globules of zinc. This can be confirmed by examining the powder by the aid of a microscope. Chemical analysis shows that in general the powder, besides metallic zinc,

' contains in varying proportions, other metals suchas lead, iron, cadmium, arsenic, etc., as well as oxygen. The oxygen is probably unlted to the zinc in such a manner that an extremely thin layer of oxid surrounds the globules of zinc. This skin of oxid, the existence of which the microscope does not reveal with absolute certainty, probably prevents the particles of zinc from re-uniting to form a liquid when running under the action of the heat, and thus renders it practically impossible to extract the metallic zinc contained. in the dust in a direct manner. Attempts have been made to re-distil the powder, either directly, or after having compressed it in the form of plates, in order to ayoid as far as possible all oxidation. But no satisfactory results have been obtained because in this case the difiiculties resulting from incomplete condensation are still present. Attempts also have been made to melt the powder and the oxidized products which contain zinc, the blue-powder for example, with ammonium chlorid (NH Cl), but as a consequence of the formation of zinc chlorid (ZnCl and of a loss of zinc resulting from this formation, the process presents numerous difficulties and it has not been considered advisable to make use of it in practice. Thus as has been already pointed out it is necessary in order to render the fusion of the powder possible to eliminate the oxide which it contains.

In order to remove the skin of oxid which prevents the powder from melting, the process according to this invention consists in treating as by washing the powder with a substance, as for example an acid, which acts on the covering of the particles thereof to form a compound soluble in water or other liquid. Preferably hydrochloric acid is used. There are several difi'erent ways of introducing the hydrochloric acid. For example: 1. In the form of vapor. 2. By the aid of a chemical substance which under certain conditions disengages hydrochloric acid, as for example, ammonium chlorid. 3.

In solution of water. Practical difliculties prevent the introduction of the hydrochloric.

ing to the proportion of oxide, there ought to be. That is to say, the metallic zinc is attacked and thus the return of metal is poor. Also it is not possible-to obtain a uniform action form hydrochloric acid except when operating on very small quantities of the products. These difliculties are avoided by utilizing the third method. The introduction of hydrochloric acid in solution in water allows the acid to be used at the exact degree of concentration desired, whereby uniform ity of action is secured.

The process involves the following operation:

- 1. The powder to be treated is shaken up with water.

2. The uantityof hydrochloric acid necessary, t e amount being determined by chemical analysis, is added to the powder after having been dilutedwith' water to the desired extent 3. After agitation, the powder is separated from the solution by decanting. This solution (with almost neutral reaction) of zincachlorid which has been formed is keptaside to be concentrated; the powder is washed in water to eliminate the excess of hydrochloric acid and of zinc chlorid.

4. The cake of powder thus obtained and which deposits easily, is compressed to drive out the water as completely as possible, and

the compressed blocks are then submitted to fusion out of contact with the air.

It is clear that any other chemical reagent which in the case we are discussing would exercise an analogous action to that of hydrochloric acid could also be utilized.

It is probable that the following reaction is produced:

This hypothesis is confirmed by theresults of analysis of the liquids coming off from the-operation, which results show thatis the transformation into metallic zinc of the powder thus treated and this either by the aid of compression only or by compresis attacked by the hydrochloric acid before the metallic zinc covered by the oxid and thus as analysis and observations have proved, very httle metallic zinc is dissolved:

Over and above a small quantity of free hydrochloric acid and of impurities the solution, almost neutral, which is obtained contains nothing but chlorid of zinc and the quantity of this product which exists is equivalent to the hydrochloric acid added. Since in order to be marketable the solution of hydrochloric acid should be relatively concentrated the solution can be returned to the cycle of operations until the degree of concentration desired has been obtained, or one can concentrate it to the desired degree. The proportion of chlorid of zinc in relation to the metallic zinc extracted varies proportionately to the density of the oxygen in the powder between admissible limits, so

that by far the most important partis extracted in the form of metallic zinc. The residue resulting from the fusion, the quantity of which, assuming the operations to be carefully conducted, is very small and consists of oxidized products containing zinc, can without any difficulty again be put through the process of manufacture.

In distinction to what takes ,place in the process. 'of distillation actually employed,

the process described above allows raw materials containing a much larger proportion of powder to be treated. It follows that many difficulties of condensation are overcome, and that in the first place, with the same consumption of coal, the capacity of the retorts is considerably lncreased. Another advantage of the process consists in the fact that it can be universally employed, whether it is a question of treating powder obtained in a special manner or of treating oxidized products containing zinc in thejfofim of blueowder. Even in these cases-the process a1 ows of the extraction of 'zine from the products, but the treatment will ilot give a good return unless the amount of oxid present does not exceed a certain percentage.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. A process for the extraction of zinc from blue-powder produced during zinc smelting which comprises treating the said powder with a substance, which acts on the covering of the particles thereof to form a compound soluble in water or other liquid and subsequently consolidating said particles.

2. A process for the extraction of zinc from blue-powder produced during zinc smelting which comprises treating the said powder with a substance which acts on thecovering of the particles thereof to form a compound soluble in water or other liquid and separating the solution from the solid paiticles of zinc and consolidating said partic es.

3. A process for the extraction of zinc from bluepowder produced during zinc smelting which comprises treating or washing the said powder with a substance which acts on the covering of the particles thereof to form a compound soluble in water or other liquid, separating the solution from the solid particles of zinc, thereafter washing the solid particles of zinc with water to remove any acid or soluble compound remaining and assembling said particles in a mass sufficiently compact to prevent an oxidation of the particles in the interior thereof.

4. A process for the extraction of zinc from bluepowder produced during zinc smelting which consists in treating the said powder with a substance which act-s on the covering of the particles thereof to form a compound soluble in water or other liquid, separating the solution from the solid particles of zinc, washing the solid particles of zinc with water to remove any acid or soluble cqmpound remaining, treating the solid zinc particles to remove moisture therefrom, and compressing and submitting them to fusion out of cont-act with air.

5. A process for the extraction of zinc from bluepowder produced during zinc smelting which comprises treating the said powder With a substance which acts on the coveringof the particles thereof to form a compound-soluble in water or other liquid, separating the solution from the solid partis cles of zinc washing the solid particles of zinc with water to remove 1 any acid or soluble compound remaining, treating the solid zinc particles to remove moisture therefrom, compressing and submitting them to fusion out of contact with air, and treating the solution separated for the extraction of the compound therefrom.

6. A process for the extraction of zinc from bluepowder produced during ,zinc smelting whlch comprises washing said powder with dilute hydrochloric acid to act on the covering of the particles thereof to form zinc chlorid which dissolves in thewater .and assembling said particles into a' compact mass. v

7. A process-for the extraction of zinc from blue-powder produced during zinc smelting which comprises washing said powder with dilute hydrochloric acid to act on thecovering of the particles thereof to form zinc chlorid which dissolves in the water, separating the solution of zinc chlorid from the solid particles of zinc remaining and fusing the particles into a mass.

8. A process for the extraction of 'zinc from blue-powder produced during zinc smelting which comprises washing the said powder with dilute hydrochloric acid to act 011 the covering of the particles to form zinc chlorid which dissolves in the water, separating the solution of zinc chlorid from the solid particles of zinc remaining, washing the solid particles of zinc with water to remove any zinc chlorid remaining and compressing it into blocks to remove moisture therefrom and submitting to fusion out of contact with air. p

9. A process for the extractionof zinc from blue-powder produced during zinc smelting which comprises washing the said powder with dilute hydrochloric acid to act on the covering of the particles thereof to form zinc chlorid which dissolves in the water, separating the solution of zinc chlo rid from the solid particles of zinc remaining, washing the solid particles of zinc with water to remove any zinc chlorid remaining, compressing it into blocks to remove moisture therefrom and submitting to fusion out of contact with air, and concentrating the solution of zinc to obtain the salt therefrom. In testimony whereof I atfix my signature in presence of two witnesses.

CHARLES VICTOR THIERRY.

Witnesses:

CLAUDIUs KUssoN, H. C. (30x11. 

